The Angolan Government has expelled hundreds of illegal foreign diamond miners in a bid to control the sector.

They had gone to Angola from neighbouring Democratic Republic of the Congo and West Africa.

During Angola's 27-year war, most of the diamond fields were controlled by the rebel Unita movement.

But Zoe Eisenstein in the capital, Luanda, says the government is now trying to increase the revenue it earns from diamond sales.

Some 700 illegal diamond miners or "garimpeiros" have been arrested in recent weeks and half have been illegal foreign immigrants.

Our correspondent say that many of the diamonds illegally mined are smuggled outside Angola and so the state does not earn any revenue from them.

"No-one knows how many 'garimpeiros' there are, no-one knows how many diamonds they are producing and no-one knows how much of what they produce goes to the state or is smuggled outside," our correspondent says.

An official from the state diamond company told our correspondent that Angolan "garimpeiros" would be registered so they could start working legally.